dm-in-dogs[/caption]Degenerative Myelopathy - Disease Basics
What is Degenerative Myelopathy?
Degenerative myelopathy is a progressive disease of the spinal cord in older dogs. The disease has an insidious onset typically between 8 and 14 years of age. It begins with a loss of coordination (ataxia) in the hind limbs. The affected dog will wobble when walking, knuckle over or drag the feet. This can first occur in one hind limb and then affect the other. As the disease progresses, the limbs become weak and the dog begins to buckle and has difficulty standing. The weakness gets progressively worse until the dog is unable to walk. The clinical course can range from 6 months to 1 year before dogs become paraplegic. If signs progress for a longer period of time, loss of urinary and fecal continence may occur and eventually weakness will develop in the front limbs. Another key feature of DM is that it is not a painful disease.
Affected brain
Degenerative myelopathy is a devastating disease causing progressive paralysis in a large number of dog breeds. New research has identified a gene that is associated with a major increase in risk of the disease.
What causes Degenerative Myelopathy?
Degenerative myelopathy begins with the spinal cord in the thoracic (chest) region. If we look under the microscope at that area of the cord from a dog that has died from DM, we see degeneration of the white matter of the spinal cord. The white matter contains fibers that transmit movement commands from the brain to the limbs and sensory information from the limbs to the brain.
DM vs Normal
In the section of a spinal cord from a dog who has died of DM (Left), the degeneration is seen as a loss of the blue color at the edges (arrows) compared with the spinal cord from a normal dog which is blue througout (Right).
This degeneration consists of both demyelination (stripping away the insulation of these fibers) and axonal loss (loss of the actual fibers), and interferes with the communication between the brain and limbs. Recent research has identified a mutation in a gene that confers a greatly increased risk of developing the disease.
How is degenerative myelopathy clinically diagnosed?
Degenerative myelopathy is a diagnosis of elimination. We look for other causes of the weakness using diagnostic tests like myelography and MRI. When we have ruled them out, we end up with a presumptive diagnosis of DM. The only way to confirm the diagnosis is to examine the spinal cord under the microscope when a necropsy (autopsy) is performed. There are degenerative changes in the spinal cord characteristic for DM and not typical for some other spinal cord disease.
What else can look like degenerative myelopathy?
Any disease that affects the dog’s spinal cord can cause similar signs of loss of coordination and weakness. Since many of these diseases can be treated effectively, it is important to pursue the necessary tests to be sure that the dog doesn’t have one of these diseases. The most common cause of hind limb weakness is herniated intervertebral disks. The disks are shock absorbers between the vertebrae in the back. When herniated, they can cause pressure on the spinal cord and weakness or paralysis. Short-legged, long back dogs are prone to slipped disks. A herniated disk can usually be detected with X-rays of the spine and myelogram or by using more advanced imaging such as CT scan or MRI. Other diseases we should consider include tumors, cysts, infections, injuries and stroke. Similar diagnostic procedures will help to diagnose most of these diseases. If necessary, your veterinarian can refer you to a board certified neurologist who can aid in diagnosing degenerative myelopathy. A directory to a neurologist near you can be found at American College of Veterinary Internal Medicine website under the "Find a Specialist Near You" link.
How do we treat degenerative myelopathy?
There are no treatments that have been clearly shown to stop or slow progression of DM. Although there are a number of approaches that have been tried or recommended on the internet, no scientific evidence exists that they work. The outlook for a dog with DM is still grave. The discovery of a gene that identifies dogs at risk for developing degenerative myelopathy could pave the way for therapeutic trials to prevent the disease from developing. Meanwhile, the quality of life of an affected dog can be improved by measures such as good nursing care, physical rehabilitation, pressure sore prevention, monitoring for urinary infections, and ways to increase mobility through use of harnesses and carts.
A Natural Approach to Managing Degenerative Myelopathy
Degenerative Myelopathy is a devastating disease. Affected dogs develop weakness in the rear legs and gradually become paralyzed. Eventually they can’t control their bowels and lose motor control on the entire upper half of the body. This degenerative process can take anywhere from six months to three years.
There is ongoing research for this disease and there is evidence suggesting that Degenerative Myelopathy is an inflammatory autoimmune disease. There is a nerve sheath (called myelin) that surrounds and insulates the nerve fibers of the spinal cord and is necessary for the conduction of nerve impulses. What happens in Degenerative Myelopathy is the dog’s own immune system cells attack the spinal cord sheath. This creates an accumulation of inflammatory cells locally and the chronic inflammation destroys the myelin sheath, leading to progressive nerve tissue damage. The damage typically begins in the middle of the back and this is where the most severe damage can be found. The nerve damage results in loss of voluntary and involuntary motor control. Some neurologists compare Degenerative Myelopathy in dogs to Multiple Sclerosis in humans.
Commonly Affected Breeds
There are about 43 breeds that have been found to have the defective gene responsible for Degenerative Myelopathy. The breeds most often affected include the German Shepherd, Boxer, Chesapeake Bay Retriever, Rhodesian Ridgeback, Irish Setter, Dalmatian, Weimaraner, Great Pyrenees, Samoyed, Briard, Siberian Husky, Miniature Poodle, Standard Poodle, Bernese Mountain Dog, Kerry Blue Terrier, Golden Retriever, Wire Fox Terrier, American Eskimo Dog, Soft-Coated Wheaten Terrier and Pug.
Diagnosis
The diagnostic tests that are normally performed are blood work (including a thyroid panel) and spinal X-rays. Other tests may include an electromyogram (EMG), MRI or CT, myelogram, and spinal tap to help rule out other spinal diseases, such as Intervertebral Disc Disease, spinal cord tumors, Degenerative Lumbosacral Syndrome, and Degenerative Joint Diseases as in Dysplasia.
If your vet highly suspects Degenerative Myelopathy, a blood sample can be submitted to the veterinary school at the University of Missouri to test for the mutant gene – or dogs can be screened with a cheek swab sample.
Symptoms
Degenerative Myelopathy initially affects the rear legs first. The dog may start to drag a foot on walks and the owner can hear or see this. The two middle nails on that weak paw may be worn down. Eventually, a lack of coordination and wobbliness in the gait is seen and the reflexes will slow in the hind feet and legs. Soon afterward, the thigh muscles will start to atrophy and the tail may be limp.
As the disease progresses, the dog will have difficulty standing for long periods of time and getting up from lying down. Fecal and urinary incontinence inevitably follow. The rear legs become so weak that the dog will need assistance to get up and he will have trouble holding a position to defecate or urinate (affected dogs often walk and poop).
As the disease progresses, the front limbs will start to become affected and weaken as well. Normally, the dog is so debilitated by this point that most patients are euthanized because of poor quality of life. Thankfully, this disease is not painful but there may be compensatory issues that will eventually cause discomfort since the dog’s biomechanics will change and tissues will be overused.
Holistic Treatments
There is no conventional veterinary medicine treatment for Degenerative Myelopathy. Holistic veterinarians use their skills and modalities to improve the quality of life. There is no need for pain meds (usually) or steroids. Treatments that do help and are readily available include acupuncture, exercise, diet and nutraceuticals.
- Acupuncture can help by stimulating the nervous system. More than likely, electroacupuncture will be used. The acupuncture needles are inserted and then small electrodes are connected to a few needles to create a microcurrent between them. This drives the acupuncture effect deeper and is very beneficial for paralyzed or partially paralyzed patients. This is performed once or twice a week for a few sessions in a row.
- Exercise is probably the most important modality for affected dogs. The nervous system has to be constantly stimulated to keep the nerve impulses firing. There is now documentation showing that physiotherapy can improve symptoms and prolongs the length of time that the dog remains mobile.
- Hydrotherapy is the safest and most effective form of exercise for these patients. Free swimming and underwater treadmill therapy have many advantages to the nervous and musculoskeletal system and the properties of water make it the safest form of exercise.
- Walks and structured therapeutic exercise are very important to maintain balance and proprioception, flexibility of the joints, keep muscles toned, and maintain good circulation. Eventually, a cart may enable the dog to remain active and maintain its quality of life once weakness or paralysis of the hind legs sets in.
The Importance of Nutrition
A balanced nutritional protocol will support the body and help control inflammation and regulate the immune system. First and foremost, the quality of protein needs to be evaluated. The higher the bioavailability of the protein, the better off the dog will be. The digestion process takes a lot of energy and creates a lot of heat which is not what the body needs, so the less work the intestines have to do, the better. Since Degenerative Myelopathy is potentially a problem with an over-reactive immune system, you want to give your dog anti-inflammatory ingredients. One of the most profound and effective is PUFAS (polyunsaturated fatty acids). They are required (essential) in the diet because they are not produced by the body. The most important is Omega-3 essential fatty acid from fish oil because it gets broken down to anti-inflammatory prostaglandins.
Inflammation anywhere in the body creates free radicals which are unstable electrons that can cause damage to cell DNA and cause cell death. Antioxidants can neutralize the free radicals and help maintain proper levels. Some antioxidants beneficial to Degenerative Myelopathy-affected dogs or to help prevent the development of the disease are: ascorbic acid (vitamin C), vitamin E, vitamin A, carotenoids, selenium, glutathione peroxidase, super oxide dismutase, coenzyme Q 10, S- Adenosyl-L-Methionine (SAMe), N-Acetylcysteine, and taurine. Most of these antioxidants are found in fresh fruits and vegetables.
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